The Areas of Investigation: 1. Cytogenetic studies of human neoplastic, hematological, and congenital disease. 2. In Vitro cytogenetic studies of direct tumor material, tissue culture lines, and colony cultures derived or established from patients with Burkitt's lymphoma, small cell carcinoma of lung, and cancer of the brain, ovary or testis. 3. Early detection of secondary leukemia in patients with non-Hodgkin's lymphoma, CLL, small cell carcinoma of lung using chromosomal abnormalities as markers. 4. Detection of sister chromatid exchanges in families with ataxia telangiectasia, Bloom's syndrome, and a high risk of cancer.